Articles | Volume 7, issue 5
Research article
06 Sep 2016
Research article |  | 06 Sep 2016

The Pollino 2012 seismic sequence: clues from continuous radon monitoring

Antonio Piersanti, Valentina Cannelli, and Gianfranco Galli

Abstract. The 2012 Pollino (Calabria, Italy) seismic sequence, culminating in the Mw 5.2 earthquake of 25 October 2012, is investigated, exploiting data collected during a long-term continuous radon monitoring experiment performed in the epicentral area from late 2011 to the end of 2014. We analyse data collected both using a phenomenological approach based on quantitative evidence and a purely numerical analysis including the following: (i) correlation and cross-correlation investigations; (ii) an original approach aimed at limiting the impact of meteorological parameters variations on the interpretation of measured radon levels; (iii) a change point analysis; (iv) the implementation of an original detection algorithm aimed at highlighting the connections between radon emission variations and major seismic events occurrence. Results from both approaches suggest that radon monitoring stations can be subject to massive site effects, especially regarding rainfall, making data interpretation harder. The availability of long-term continuous measurements is crucial to precisely assess those effects. Nevertheless, statistical analysis shows a viable approach for quantitatively relating radon emanation variations to seismic energy release. Although much work is still needed to make radon time series analysis a robust complement to traditional seismological tools, this work has identified a characteristic variation in radon exhalation during the preparation process of large earthquakes.

Short summary
We investigate in an innovative way the dynamics of radon emanation in a seismically active area. We analysed 3 years of data, collected during a long-term radon monitoring experiment. The complexity of the relationships among the investigated variables led us to consider the problem both from a phenomenological point of view and by means of original numerical analyses. Different approaches converge on the existence of a physical relation between soil radon emanation and seismicity.